When you've got abundant power at 3.73 for pulling grades, why change a good thing? All Dmax HDs from the beginning (2001) are 3.73 from the factory. Only the gasser HDs were 4.10 rears. Newer model gassers now offer both rears.

I don't understand how so many of you guys get such good mileage. Makes me wonder if my truck and everybody I personally know with duramax pickups have something wrong with them. The tires on my pickup are about 36" tall and the best I have ever got is 17 mpg. I went on a camping trip one time pulling a 30' camp trailer at about 8,000 lbs and I drove 1000 miles round trip. I used exactly 100 gallons of fuel on that trip. My math says 10 mpg. I have a friend with an LB7 02' 1 ton that does hot shot loads for a living and he gets 8 mpg average. My brother has a bone stock 06' LLY and he gets 15 mpg average. I am confused.

I get about 17mpg hwy, 12-13 city on winter fuel. Since using fuel additive numbers have gone up, but only by ~1mpg. My LBZ is stock, no lift, and is on 235/85r16 toyo wlt1 winter tires, stock alloys. 100km/h on the highway, being non-aggressive.

I'll post up if there's a change when I get rid of my current fuel filter (12% and falling fast)

I don't understand how so many of you guys get such good mileage. Makes me wonder if my truck and everybody I personally know with duramax pickups have something wrong with them. The tires on my pickup are about 36" tall and the best I have ever got is 17 mpg. I went on a camping trip one time pulling a 30' camp trailer at about 8,000 lbs and I drove 1000 miles round trip. I used exactly 100 gallons of fuel on that trip. My math says 10 mpg. I have a friend with an LB7 02' 1 ton that does hot shot loads for a living and he gets 8 mpg average. My brother has a bone stock 06' LLY and he gets 15 mpg average. I am confused.

You really have to take mpg threads with a grain of salt.
Everyone has different driving habits/styles, so mileage varies greatly.
Some have their truck tuned/programmed some dont.
Some are pretty accurate with their numbers some arent.
Those 36" tires are probably hurting your mpgs. Is your speedo calibrated for the taller tire?

So far through the winter her in MN my truck is still on the 265s and my mpg with the efi live tunes have been 14.8-15.5 thats running the 100hp performance tune. I lose about 1.5mpg running the 150hp race tune and lose about .6mpg running the 75hp economy tune.

So for leaving my truck idle for about 2 hours a day in -20 to 20 temps and doing mixed driving for 45miles every day I'm not too disapointed.

Thats all hand calculated by gps and dash. Idaho Rob got my ODO set perfect for the 265s, its only been off by 1/10 of a mile per tank.

You really have to take mpg threads with a grain of salt.
Everyone has different driving habits/styles, so mileage varies greatly.
Some have their truck tuned/programmed some dont.
Some are pretty accurate with their numbers some arent.
Those 36" tires are probably hurting your mpgs. Is your speedo calibrated for the taller tire?

I am not complaining about my mileage, I didn't expect 20 mpg when I have a pickup with 36" tires on it. I just think that people are adding a couple mpg's to their actual miles. When my pickup gets 10 mpg with 36" tires pulling an 8000 lb trailer and I see people posting 19 mpg pulling 18000 lbs, it makes me wonder.

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